Guided Open-Loop System for Deep Space Doppler Tracking

High accuracy and real-time Doppler frequency estimation in deep space is essential for spacecraft ranging, orbit determination and planetary atmospheric measurement. Considering the problems of frequent lose-lock, high processing cost and performance degradation of current systems, an open-loop tracking system guided by the on-line self-calibrating trajectory model is proposed to achieve deep space high accuracy real-time Doppler frequency estimation. It includes a tracking guidance model to predict the target Doppler frequency changing for signal dynamic compensation and reduce the residual frequency estimation complexity, and a multi-stages residual estimation module to improve the frequency tracking accuracy. The proposed scheme is validated by both simulation test and actual space experiment data. The real-time frequency tracking error in simulation is 75.9mHz while the tracking residuals of MEX data is 3.7~7.1mHz. It shows competitive performance to post processing schemes with mHz class accuracy.